The present invention generally relates to wet electrostatic precipitators and more particularly concerns to wet electrostatic precipitators of the type that include a flat discharge electrode structure that is vertically suspended from an overhead support structure.
In wet electrostatic precipitators of the type shown, for example, in U.S. Pat. No. 4,181,509, the discharge electrodes and collector plates have annular shapes and are vertically arranged in concentric relationships. The discharge electrodes are suspended from an overhead support structure so that the lower ends are not connected to a support. Due to the inherent rigidity in the annular shape of the electrodes, there has been no problem regarding oscillation of the lower ends of the discharge electrodes.
Trade literature by the Mikropul Corporation entitled, Elektrofil Wet Electrostatic Precipitators, discloses another type of wet electrostatic precipitator in which the discharge electrodes and collector plates are flat and are vertically arranged in uniformly spaced, parallel relationships. The flat discharge electrodes are as in the aforementioned patent, suspended only from their upper ends.
Trade literature by the Envirotech Corporation entitled, Fluid-Ionics Systems Fluid-Plate Modular Wet Precipitator, discloses a wet electrostatic precipitator including flat discharge electrodes and collector plates vertically arranged in uniform spacings. The discharge electrodes are suspended from a pair of support tubes made from conductive metal, and a potential is applied to the tubes to charge the discharge electrodes. The precipitator further includes a housing surrounding the electrodes, air inlet and outlet hoods mounted to the top and bottom of the housing, respectively, and scrubber sprayers mounted to the inlet hood.
A major problem that has occurred in the testing of the wet electrostatic precipitator of type shown in the last-mentioned article concerns the oscillation or swinging of the lower ends of the discharge electrodes. It has been observed that the sparking that sometimes occurs between the lower ends of a discharge electrode and collector plate can cause the flat electrodes to sway. Such swaying sometimes can increase in magnitude so that the sparking is so great that the electrostatic field is reduced below the voltage level required for proper precipitation action.
It has been found that this spark-induced oscillation problem cannot be easily cured by simply connecting the lower ends of the discharge electrodes to the housing or cross members thereat. Since the precipitator is operated wet, i.e., liquid is constantly flowing downwardly over the collection plates and dripping from the discharge electrodes, a rigid connection to the lower ends of the electrodes--no matter how well electrically insulated--would become covered with liquid, thus providing a leak path to ground potential.
U.S. Pat. No. 4,167,400 shows a electrode restraining assembly intended for use in a dry electrostatic precipitator. The device includes a grid attached to nonconductive plates that are, in turn, attached to the sidewalls of the precipitator. The discharge electrodes are comprised of wiring and weights are suspended from the wires.
U.S. Pat. No. 4,189,308 describes the aforementioned sparking phenomenon in connection with a parallel plate type of wet electrostatic precipitator.